Fixed arithmetic error in calculating read offset for direct IO

wordfence/scanning/scanner.py

@@ -408,8 +408,7 @@ def __init__(
         self._logging_initializer = logging_initializer
         self._profile = profile
         self._opener = self._open_direct if direct_io else self._open
-        if direct_io:
-            self._direct_io_buffer = DirectIoBuffer(self._chunk_size)
+        self._direct_io = direct_io
         self.complete = Value(c_bool, False)
         self._timer = None
         super().__init__(name=self._generate_name())
@@ -429,6 +428,8 @@ def work(self):
                 'scan_worker',
                 is_global=True
             )
+        if self._direct_io:
+            self._direct_io_buffer = DirectIoBuffer(self._chunk_size)
         try:
             self._working = True
             self._matcher.prepare(thread=True)

wordfence/util/direct_io.py

@@ -31,7 +31,7 @@ def __init__(self, path: str, buffer: DirectIoBuffer):
         self.offset = 0
 
     def read(self, limit: Optional[int] = None) -> bytes:
-        read_offset = math.floor(self.offset / mmap.PAGESIZE)
+        read_offset = math.floor(self.offset / mmap.PAGESIZE) * mmap.PAGESIZE
         skip = self.offset % mmap.PAGESIZE
         read_length = os.preadv(self.fd, self.buffer.buffers, read_offset)
         read_length -= skip